The invention relates to an electric lamp comprising:
an envelope of a light-transmitting material with a neck and a light source;
a lamp cap provided with contacts and fixed around a free end portion of the neck; and
current conductors extending from the light source through the free end portion of the neck and electrically connected to the contacts of the lamp cap.
Such an electric lamp is known from EP-0 758 486. The known lamp is a reflector lamp because the envelope is internally partly reflectorized. The light source in the known lamp is mechanically fixed in a plate. The plate and the light source are fixed in the neck of the envelope by means of cement. The current conductors passed through the free end portion of the neck issue into the lamp cap, which is hollow. The lamp cap has a helically threaded contact around its axis and a central contact situated on its axis. The current conductors of the light source are flexible and are guided towards the contacts of the lamp cap in the hollow lamp cap, for example in that they are bent, and are fixed to these contacts by means of welding or soldering.
It is a disadvantage of the known lamp that the creation of the electrical contact between the current conductors of the light source and the contacts of the lamp cap by welding or soldering is a comparatively labor-intensive and cumbersome process. This process is also made more difficult by the size of the light source, which leaves comparatively little space for achieving the contacting. In addition, welding or soldering is a process which is comparatively bad for the environment. An undesirable bending of the flexible current conductors may take place as a result of external forces, such as shocks and impacts, because the current conductors in the hollow lamp cap of the known lamp are not screened off from one another. This means that the known lamp has the additional disadvantage that there is a comparatively high risk of short-circuiting in that the current conductors approach one another too closely, or even touch one another, owing to the inadvertent bending.
It is an object of the invention to provide an electric lamp of the kind described in the opening paragraph which has a comparatively safe construction and which renders possible a simple assembly of the lamp.
According to the invention, this object is achieved in that an insulator body provided with connection conductors is accommodated in the lamp cap for electrically interconnecting the current conductors and the contacts of the lamp cap. The connection conductors are guided through the insulator body through respective channels. The channels are separated from one another. The current conductors and the connection conductors electrically connected thereto are mechanically screened from one another by the insulator body in this way. This renders the lamp comparatively safe because the risk of short-circuiting through the current conductors touching each other has been reduced. The channels in the insulator body comprise recesses. An end of the connection conductor, which comprises, for example, a ferrule, extends into this recess, while another end of the connection conductor is electrically connected to the contact of the lamp cap, for example by means of a resilient contact. The resilient contact has the advantage that the electrical connection between the connection conductor and the contact on the lamp cap can be achieved without welding or soldering. This simplifies lamp assembly and is better for the environment. The current conductor makes electrical contact with the connection conductor in that it is inserted as far as possible into the recess. The electrical contacting of the current conductor with the contact on the lamp cap via the connection conductor is thus achieved in a comparatively simple manner. This further simplifies the lamp assembly.
In an embodiment, the envelope is internally reflectorized between the neck and the light emission window. The reflector body thus formed has a concave light-concentrating portion with an optical center and is present between the neck and the light emission window. The light source is arranged axially in the optical center. The light generated by the light source can be formed into a beam and aimed in a simple manner by means of the reflector body of the reflector lamp thus obtained.
In an embodiment, the insulator body is made of synthetic resin, porcelain, glass, or a ceramic material. It is favorable for the use of the lamp at comparatively high temperatures when the insulator body is made of porcelain, glass, or ceramic material on account of the good temperature resistance of porcelain, glass, and ceramic material. If the lamp is to be used at comparatively low temperatures, the insulator body is preferably made of a synthetic resin because an insulator body of synthetic resin can be simply and inexpensively manufactured.
It is favorable for a reproducible position of the insulator body in the lamp cap when the insulator body is provided with a recess which cooperates with the lamp cap. The insulator body is secured in the lamp cap in that the lamp cap is indented into said recess. The insulator body and the lamp cap are locked thereby against a mutual rotation about the axis. Such a rotation may occur as a result of torsional forces, for example while the lamp is being screwed into or from a luminaire. In addition, the assembly of the electric lamp is further simplified thereby because an additional position definition of the insulator body in the lamp cap with respect to the light source is avoided. Furthermore, the risk is reduced that short-circuits may arise between the current conductors in the lamp cap owing to a rotation of the insulator body with respect to the lamp cap.
In a favorable embodiment of the electric lamp, the connection conductor comprises a first end which is chosen from a group formed by resilient clamps and scraping contacts. The advantage of such a first end is that it has a clamping and fixing action whereby the current conductor is retained therein. The risk that the electrical contact between the current conductor and the contact on the lamp cap will be broken is reduced in this manner.
The light source in the known lamp is aligned and fixed in the neck of the envelope by means of cement, for example lamp cement. It is a disadvantage in the case of a reflector lamp, however, that cement, also after curing, evolves volatile components which may reduce the reflecting power of the reflector body. In the lamp according to the invention, the use of cement for this purpose is avoided because a reproducible fixed position of the insulator body in the lamp cap is achieved in that the insulator body is enclosed with narrow fit in the lamp cap. For this purpose, the insulator body may have, for example, a helically threaded surface, in which case the insulator body can be screwed into the lamp cap, which comprises a helically threaded contact, in a rotational movement. Since the insulator body is fixed in the lamp cap, it has become possible to fix the light source aligned in the reflector lamp in conjunction with the clamping/fixing first end. A yet further simplification in the lamp assembly is achieved as well thereby.
In a further favorable embodiment of the electric lamp, at least one connection conductor comprises at the same time one contact of the lamp cap. Since a separate welding or soldering operation for the electrical connection of the connection conductor and the contact of the lamp cap is avoided, the assembly of the lamp is still further simplified and has a lesser impact on the environment. In addition, an even more reliable electrical contacting is achieved in this way.
The light source may be an incandescent body, possibly in an atmosphere comprising halogen, or a discharge path between electrodes in an ionizable medium, for example metal halides in rare gas, possibly with mercury. The lamp vessel may be made from glass, for example hard glass or glass with an SiO2 content of at least 95% by weight such as, for example, quartz glass, or monocrystalline or polycrystalline material such as, for example, aluminum oxide. The lamp vessel may be surrounded by an outer bulb.
The reflector lamp may be provided with a light-transmitting cover which is fastened to the reflector body and which closes off the light emission window.